Pentagonal Bipyramid Fe Complexes: Robust Ising-Spin Units towards Heteropolynuclear Nanomagnets.

Pentagonal bipyramid Fe complexes have been investigated to evaluate their potential as Ising-spin building units for the preparation of heteropolynuclear complexes that are likely to behave as single-molecule magnets (SMMs). The considered monometallic complexes were prepared from the association of a divalent metal ion with pentadentate ligands that have a 2,6-diacetylpyridine bis(hydrazone) core (H L ). Their magnetic anisotropy was established by magnetometry to reveal their zero-field splitting (ZFS) parameter D, which ranged between -4 and -13 cm and was found to be modulated by the apical ligands (ROH versus Cl).

Heptacoordinated nickel(II) as an Ising-type anisotropic building unit: illustration with a pentanuclear [(NiL)3{W(CN)8}2] complex.

Heptacoordinated nickel(II) complexes characterized by substantial Ising-type single-ion anisotropy have been involved in the construction of two pentanuclear [Ni3W2] compounds by association with [W(CN)8](3-). For one of them, slow relaxation of magnetization was observed to occur concomitantly with antiferromagnetic ordering.